Manufacture of viscose rayon



United States Patent Ofifice 3,026,170 Patented Mar. 20, 1962 Thepresent invention relates to the manufacture of rayon yarns, filaments,films and the like and more particularly to the production of hightenacity viscose rayon yarn, that is characterized by its high tenacitywhich makes it especially suitable for use in reinforcing rubberarticles such as cord tires and the like.

Due to extensive research being conducted by various rayon manufacturersin recent times, improvements in the physical properties of rayon havebeen and are being made. These improvements consist of, for example,increasing the breaking st-rength and elongation at the break of thethread, increasing Wet and dry strengths, lowering of the secondaryswelling, and increasing the resistance to flex fatigue, abrasion andsoiling. Most of the recent improvements seem to bear relationship withthe formation of a thread having skin throughout most or all of itscross-section, which indicates, at least, that the molecularcrystallinity of the thread has been changed.

Perhaps, the most important recent development is the use of specialadditives in the spinning system, preferably in the viscose. The precisetheory of how the additives affect the coagulation and regeneration ofcellulose in the viscose to produce an improved thread has not beendefinitely established, with various and different views having beenexpressed. However, it is known that these additives, now referred to asviscose modifiers in the art, tend to retard the regeneration andcontribute to the formation of filaments having a large degree of skinand a crosssection with a relatively smooth uncrenulated surface.

Among the first known viscose modifiers, there were included certainaliphatic monoamines and certain quaternary ammonium compounds asdisclosed in U.S. Patents 2,535,044, 2,535,045 and 2,536,014. Otheradditives having in part or the same effect as the aforesaid amineadditives are known.

It is known to employ polymerized alkylene oxides as spinning assistantsin the spinbath in extremely small amounts to prevent the clogging ofspinneret orifices as disclosed in U.S. Patent 2,442,331. Moreover, itis disclosed in Belgian Patent 547,681 that polyethylene oxide with amedium molecular weight of 300l0,000 when added to the viscose inamounts of 05-19% by weight of the cellulose influences the formation ofviscose rayon filaments of the skin-type with non-crenulated surfacesand high strength. Also, it is disclosed in U.S. Patent 2,696,423 thatthe combination of the polyethylene oxide compounds having a molecularweight of from about 300 to 1000, among other ether-type modifiers, maybe admixed with certain dithiocarbamate modifiers to increase themodification thereof. It is to be understood that the use ofpolyalkylene oxide compounds as spinning assistants or as per se aviscose modifier forms no part of the present invention.

There is disclosed in copending application Serial No. 609,792, filedSeptember 14, 1956, and having common ownership herewith, a process forthe manufacture of high strength yarn, whereby viscose is spun into aspinbath, the acid content of which is low enough to entail heavy zincand sulfur containing deposits in and around the spinbath container sothat spinning becomes impractical, characterized in that the spinningprocess is carried out in the presence of a sufliciently large quantityof certain ethoxylated cation-active quaternary ammonium compounds tobring about a modification of the regeneration of the cellulose, whilesimultaneously preventing the formation of the undesirable deposits.These amine additives are called Ethoquads; and the yarn so produced hasexcellent fatigue resistance and remarkable strength values, especiallysuitable for tire cords.

The Ethoquad viscose modifier disclosed in said copending applicationhas the following general formula:

where R and R represent preferably an alkyl radical but may include ana-ryl or alicyclic radical with R preferably being an alkyl radicalcontaining six or more carbon atoms and R being an alkyl radicalcontaining one to three carbon atoms; Z represents an anion havingsubstantially no surface activity such as hydroxide, halide, sulfate,acetate, etc.; x and y are whole numbers of at least one with thepreferred combined value of x and y being 2 to 50 or more; n is a wholenumber, possibly one but preferably two and no more than four. However,in practice, it was found that for a set of given spinning conditionsthere existed an optimum concentration above which the use of theEthoquad gave very little or no additional improved modification.Therefore, it was thought that the use of the additives as modifiers hadcertain limitations. While the known modifiers are useful and influence,in a favorable manner, the formation of yarn having improved properties,it is desired to obtain further improvement in the properties, such asimproved cord strength. it is recognized that the tenacity of viscoserayon yarn considerably diminishes when processed into a cord, forexample, a the cord. j It is an object of the present invention toprovide a method for the manufacture of filamentsof regeneratedcellulose by the viscose process which have improved physical propertiesin general and which may be twisted and plied into a cord constructionwith a minimum loss in tenacity.

It is another object of the present invention to provide a viscosespinning composition containing a novel combination of modifiers fromwhich viscose rayon yarn of improved physical properties may be spun.

Other objects and advantages of the present invention will becomeapparent herein.

In a very surprising manner, it was found that the aforesaid objects areaccomplished by spinning viscose that contains a synergistic combinationof additives con sisting of certain polyethylene oxide compounds and certain ethoxylated cation-active quaternary ammonium. compounds in amountsto bring about a modification of the cellulose that results in theproduction of viscose rayon filaments having improved properties ascompared to filaments produced under the influence of either type ofadditive when employed singularly. The viscose containing thecombination of additive is spun according to the viscose process intofilaments in an aqueous acidic coagulating oath containing a Zinc salt.Thereafter, the filaments are given a high degree of stretch beforecomplete regeneration thereof.

The degree of polymerization of the polyethylene oxide additives mayvary depending upon the spinning conditions and the other additivesemployed. However, the improvement of the present invention is attainedonly when the molecular weight of the polymerized ethylene oxide lies inthe range of about 1500-4500. Below the lower limit the modifying powerdiminishes; above the upper limit the additive may not dissolve in theviscose to a required minimum quantity. It has been found that thepolyethylene oxide compounds induce the desired modifying effect whenadded to the viscose in amounts of O.55.0% by weight based on thecellulose content in the viscose, hereinafter referred to in short as(C.I.V.).

In general, the quaternary ammonium compounds contemplated to beincorporated in the viscose with the polyethylene oxide compounds arethe socalled Ethoquads as described above in detail. More particularly,the viscose modifier for this purpose has the following general formula:

where R is an alkyl radical with at least 6 carbon atoms; x+y=250; and Zis an innocuous anion. The amount of the just described additive shouldbe used in the range of 0.55.0% (C.I.V.) in order to obtain the desiredoptimum modifying effect.

It is essential to the invention that the combination of thepolyethylene oxide compounds and the ethoxylated cation-activequaternary ammonium compounds be employed in a minimum totalconcentration of at least 2.0% (C.I.V.), otherwise, the enhancedmodification will not be attained.

The viscose containing the aforesaid combination may have othermaterials, such as delustrants, incorporated therein and may be preparedin part or in whole from wood pulp, with the degree of maturity. and thepercentages of cellulose and alkali of the viscose not being especially.critical. But better results are obtainable when the viscosecontainsfrom 5.5 to 8.0% cellulose and from 4.0 to' 6.0% alkali and hasa maturity in the range of l'18 NH Cl number. Generally these variablesare correlative with each other, but not strictly so in order. to obtainthe improved yarn properties of the present invention, depending uponthe other spinning constants. The modifiers may be incorporated in thespinning system in a variety of ways, such as by adding the additivesduring the dissolving operation or by injecting the additives into astream of viscose being pumped to. the spinneret.

The coagulating bath into which this viscose is extruded through aspinneret immersed therein should cont-ain a soluble zinc salt, such aszinc sulfate in the amount of not less than 2%, preferably 3.5% andmore. Moreover, the sulfuric acid concentration of the bath may and forbetter results should be lower than concentrations ordinarily usedinviscose rayon production. For example, the amount of acid should be lessthan 7% with the maintenance of a minimum concentration suificient tocoagulate and partially regenerate the cellulose. Other salts, such assodium sulfate and spinning assistants are also contained in thespinbath. Preferably, the spinbath should have a temperature of about 40to 70 C. The length of. thread immersion depends upon the spinning speedas well as the particular spinbath employed. Since regeneration isretarded under the spinning conditions described herein, it is preferredto conduct the thread through a spinning tube, of the type described inU.S. Patent No. 2,908,937. As shown therein, the thread is passedthroughthe tube during at least part of its travel in the spinbath.

After being withdrawn from the spinbath in a conventional manner, thefreshly spun viscose thread is stretched in the excess of 50%,preferably by 80100% or higher. To, obtain the best results, the stretchis applied in a weakly acidic second bath at a temperature, preferablyabove 80 C., and best at 95 C. The thread is then takenup in packageform and aftertreated, or aftertreated in a continuous. fashion and thentaken up in package form.

The thread produced in accordance with the present invention isparticularly characterized by its very low loss in tenacity when twistedinto cord. In addition, the thread has lower secondary swelling,increased resistance to flex fatigue and other improvements which makeit especially suitable for use as reinforcing cords in tires, conveyorbelts, etc. Furthermore, the thread has the socalled skin structure andnon-crenulated surfaces associated with thread produced under theinfluence of a viscose modifier.

The following examples are illustrative of the practice of the presentinvention as described herein. All concentrations unless otherwise notedare calculated as percentages by weight based on the viscose or thespinbath.

EXAMPLE I Alkali cellulose was prepared in the conventional manner fromwood pulp to obtain the desired degree of polywherein.x+y=approximately15 ethylene oxide units and R is a saturated straight chain hydrocarbonradical containing 8-18 carbon atoms in the amount of 1.0% (C.I.V.) andpolymerized ethylene oxide having an average molecular weight of about4000 in the amount of 1.0% (C.I.V.) were added.

The viscose containing the just mentioned combination of additives waspermitted to age to a maturity value of 1416 NH CI number. Afterconventional filtering and deaerating, the viscose was formed into athread of 1650 denier, 720 filament viscose rayon yarn by extrusion ofthe viscose through a spinneret into an aqueous coagulating bath havinga temperature of 65 C. and containing 4.8% H 50 12% Na SO and 3.5% ZnSOAfter being passed through the coagulating bath, the thread waswithdrawn therefrom by means of a first godet. Then the thread wasguided into and through a second hot weakly acidic bath at a temperatureof 94 C. and withdrawn therefrom by means of a second godet. Due to apredetermined differential in the peripheral speeds of said godcts, thethread was stretched 98% therebetween. The yarndraw off speed was 55meters per minute. The aftertreatrnentv ofthe thread was carried outaccording to the usual processes which includes drying of the thread.Then the thread was given a slashing stretch of about 12% and thereafterdried under tension. The slashed thread was twisted and plied into thetire cord construction of 11.4 x 10.6.

For comparison purposes, threads were produced under the same conditionsmentioned above in this example except that the sole additive employedwas the polyethylene oxide compound of the present example in the amountof 2.0% (C.I.V.). Moreover, threads were also produced under theseconditions but while using only the quaternary amine additive of thepresent example in the amount of 2.5% (C.I.V.).

The strength properties of the threads so produced are listed in Table Ifor comparison, from which it is seen that according to the presentinvention there is a significant increase in both the conditioned andoven dry cord properties;

EXAMPLE H A viscose having a composition of 7.5% cellulose and 5.5%total alkalinity was prepared in the manner described in Example I. Tothis viscose the ethoxylated quaternary amine and the polyethylene oxideadditives used in Example I were added in the amounts of 2.0% (C.I.V.)and 1.0% (C.I.V.), respectively. After aging, filtering and deaerating,the viscose was formed into a thread of 1650 denier, 720 filamentviscose rayon yarn by extrusion through a spinneret into an aqueousacidic coagulating bath having a temperature of 51 C. and containing5.2% H 80 12% Na SO and 5.0% 2.1180

After being passed through the coagulating bath, the thread waswithdrawn therefrom by means of a first godet. Then, the thread wasguided into and through a second hot weakly acidic bath at a temperatureof 94 C. and withdrawn therefrom by means of a second godet. Due to apredetermined diiferential in the peripheral speeds of said godets, thethread was stretched 100% therebetween. The yarn draw-off speed was 65meters per minute. The aftertreating of the thread was carried outaccording to the usual processes. Then the thread was given a slashingstretch of about 12% and thereafter dried under tension. The slashedthread was plied into the tire cord construction of 12.0 x 12.0.

For comparison purposes, threads were produced under the same conditionsmentioned above in this example except that the sole additive employedwas the polyethylene oxide compound of the present example in the amountof 2.0% (C.I.V.). Moreover, threads were also produced under theseconditions while using only the quaternary amine additive of the presentexample in the amount of 2.7% (C.I.V.).

The strength properties of the threads so produced are listed in TableII for comparison, from which it is seen that according to the presentinvention there is a significant increase in both the conditioned andoven dry cord properties.

Table II Quaternary Polyethyl- Strength, g./100 den. amine+ Quaternaryene oxide A viscose having a composition of 7.5 cellulose and 5.7% totalalkalinity was prepared in the manner described in Example I. Theviscose after being properly filtered, deaerated and aged was pumped toa spinneret through a conduit. A solution containing the combination ofadditives used in Example I was injected and later intimately mixed inthe amounts of 1.5% (C.I.V.) ethoxylated quaternary amine and 1.0%(C.I.V.) poly- .cthylene oxide into the viscose in the manner describedin copending application Serial No. 655,004, filed April 25, 1957, andhaving common ownership herewith.

The viscose containing the additives was formed into a thread of 1650denier, 1100 filament viscose rayon yarn 6 in an aqueous acidiccoagulating bath having a temperature of 55 C. and containing 4.7% H 12%Na SO and 4.4% ZnSO The freshly spun thread was stretched 93%,aftertreated and slash stretched as described in Example 11. The threadwas then plied into the tire cord construction of 11.4 x 10.6.

For comparison purposes, threads were produced under the same conditionsmentioned above in this example except that the sole additive employedwas the polyethylene oxide compound of the present example in the amountof 2.0% (C.I.V.). Moreover, threads were also produced under theseconditions while using only the quaternary amine additive of the presentexample in the amount of 2.0% (C.I.V.).

The strength properties of the threads so produced are listed in TableIII for comparison from which it is seen that there is a significantincrease in conditioned and oven dry cord properties and in wet slashedsingles strength.

EXAMPLE IV A viscose having a composition of 7.5 cellulose and 5.6%total alkalinity was prepared in the manner described in Example I. Tothis viscose the ethoxylated quaternary amine and the polyethylene oxideadditives used in Example I were added in the amounts of 1.5% (C.I.V.)and 0.5% (C.I.V.), respectively. After aging, filtering and deaerating,the viscose was formed into a thread of 1100 denier, 720 filament in anaqueous acidic coagulating bath having a temperature of 55 C. andcontaining 4.6% H 50 12% Na SO and 4.4% ZnSO The freshly spun thread wasstretched 98%, aftertreated and slash stretched as described in ExampleII. The

' thread was then plied into the tire cord construction of Table 1 VQuaternary Strength, g./100 den. amine Quaternary polyethylamine onlyene oxide Unslashed singles, conditioned 444 425 Slashed singles,conditioned 483 465 Slashed singles, wet 343 320 Cords, conditioned 422384 Cords, oven dry 515 451 EXAMPLE V A viscose having the compositionof 7.5% cellulose and 5.6% total alkalinity Was prepared in the mannerdescribed in Example I. Polymerized ethylene oxide having an averagemolecular weight of 2000 in the amount of 1.5% (C.I.V.) and theethoxylated quaternary amine used in Example I in the amount of 0.5%(C.I.V.) were added to a portion of the viscose. To another portion ofthe viscose polymerized ethylene oxide having an average molecularweight of 1000 in the amount of 1.0% ('ClV.) and the ethoxylatedquaternary amine used in Example I in the amount of 1.0% (C.I.V.) wereadded. To a third portion of the viscose polymerized ethylene oxidehaving an average molecular weight of 1000 in the amount of 2.5% C.I.V.)was added.

These viscoses were produced into threads in a manner identical'toExample IV. The strength values of these threads are reported in Table Vfrom which it is seen that the tenacities of the threads produced usingpoly ethylene oxide having the lower molecular Weight of 1000, eitheralone or together with the quaternary amine were considerably lower ascompared to the tenacities of the thread produced under the influence ofboth the polyethylene oxide compound having the molecular weight of 2000and the quaternary amine in accordance with the present invention.

Table V 1.5% (C.I.V.) 1.0% (C.I.V.) Polyethylene Polyethylene 2.5%(C.I.V.) oxide (M.W.= oxide (M.W.= Polyethylene Strength, g./l den.2,000)+0.5% 1,000)+1.0% ox1de(M.\

(C.I.V.) (C.I.V.) 1,000) only quaternary quaternary amine amineUnslashed Singles,

conditioned 463 470 458 Slashed singles, conditioned 504 486 485 Slashedsingles, wet- 347' 338 331 Cords, conditioned." 415 395 395 Cords, ovendry 494 484 471 where R is an alkyl radical with at least 6 carbonatoms; x+y=250 and Z is an innocuous anion, in the amount of 0.5 to 5.0%by weight based on the cellulose content 7 and polyethylene oxide havinga molecular weight in the range of 1500-4500 in the amount of 0.5 to5.0% by weight based on the cellulose. content, the totaljminimum amountof said compound and polyethylene oxide being at least 2.0% by Weightbased on the cellulose content, into an aqueous spinbath containing lessthan 7 sulfuric acid and at least 2% zinc sulfate and stretching thefreshly spun thread.

2. A method of producing viscose rayon filaments having improvedstrength comprising adding to a viscose the methyl chloride quaternaryderivative of an ethoxylated quaternary ammonium compound, having thegeneral formula:

wherein x+y=approxirnately 15 and R is a saturated, straight chain,hydrocarbon radical containing 8-18 carbon atoms in the amount of about1-2% by Weight based on the cellulose content and polyethylene oxidehaving a molecular Weight in the range of 15004500 in the amount ofabout 0.5-1.0% by Weight based on the cellulose content, the totalminimum amount of said compound and polyethylene oxide being at least2.0% by weight based on the cellulose content, spinning the resultingviscose into a thread in an aqueous coagulating bath containing lessthan 7% sulfuric acid and at least 2% zinc sulfate, and passing thefreshly spun thread into a second weakly acidic bath at a temperatureabove C. while stretching the thread to the extent of at least 80%.

3. A viscose spinning composition containing a compound having thegeneral formula:

Where R is an alkyl radical with at least 6 carbon atoms; x+y=2-50 and Zis an innocuous anion, in the amount of 0.5 to 5.0% by weight based onthe cellulose content and polyethylene oxidehaving a molecular weight inthe range of 1500-4500 in the amount of 0.5-5.0% by weight based onthecellulose content, the total minimum amount of said. compound andpolyethylene oxide being at least 2.0% byweight based on the cellulosecontent.

4. A viscose spinning composition. containing an ethoxylated quaternaryammonium compound, having the general formula:

where x+y=approximately 15 and R is a saturated, straight chain,hydrocarbon radical containing 8-18 carbon atoms in the amount of about12% by weight based on the cellulose contentand polyethylene oxidehaving a molecular weight in the range of 15004500 in the amount ofabout 0.51.0% by weight based on the cellulose content, the totalminimum amount of said compound and polyethylene oxide being at least2.0% by Weight based on the cellulose content.

References Cited in the file of this patent UNITED STATES PATENTS2,572,217 Thurmond Oct. 23, 1951 2,593,466 MacLaurin Apr. 22, 19522,648,611 Richter Aug. 11, 1953 2,696,423 Dietrich Dec. 7, 19542,705,184 Drisch Mar. 29, 1955 2,732,279 Tachikawa Jan. 24, 19562,759,975 Chiddix Aug. 21, 1956 2,852,334 Hollihan Sept. 16, 19582,860,480 Cox Nov. 18, 1958 2,937,922 Mitchell'et a1. May 24, 1960

1. A METHOD OF PRODUCING VISCOSE RAYON FILAMENTS HAVING IMPROVEDSTRENGTH COMPRISING SPINNING A THREAD FROM A VISCOSE CONTAINING ACOMPOUND HAVING THE GENERAL FORMULA: